[Document upload] fix date parsing

1 job for !184 with 561-dev-document-date in 27 seconds (queued for 9 minutes and 30 seconds)
detached
Status Job ID Name Coverage
  Docs
failed #8060
allowed to fail
docs

00:00:27

 
Name Stage Failure
failed
docs Docs
zlib-bindings-0.1.1.5: database=snapshot, source=zlib-bindings (from Hackage), after: zlib-0.6.2.3
zstd-0.1.3.0: database=snapshot, source=zstd (from Hackage)

No executables to be installed.
$ cp -R "$(stack path --local-install-root)"/doc ./output
/usr/bin/bash: line 117: stack: command not found
cp: cannot stat '/doc': No such file or directory
Cleaning up file based variables
ERROR: Job failed: exit code 1